On Thu, 21 Apr 2011, Leonardo M. Ramé wrote:
--- On Thu, 4/21/11, Marco van de Voort <mar...@stack.nl> wrote:
From: Marco van de Voort <mar...@stack.nl>
Subject: Re: [fpc-pascal] FPImage and GetDataLineStart
To: "FPC-Pascal users discussions" <fpc-pascal@lists.freepascal.org>
Date: Thursday, April 21, 2011, 6:41 AM
In our previous episode, Sven Barth
said:
> Am 20.04.2011 22:20, schrieb Leonardo M. Ram?:
> > Hi, I need to write a function that replaces
TLazIntfImage by using fpImage, and I can't find an
alternative to GetDataLineStart. How can I replace it?.
>
> Maybe I get your intention wrong, but TLazIntfImage is
already using
> fpImage and it derives from a TFPCustomImage itself.
True, but TFPCustomImage is abstact wrt memory layout and
doens't provide
row level access, only pixel level access.
Only TFPMemoryImage adds the memory access, but IIRC only
64-bit pixels.
(16-bit RGBA)
While these abstractions make it easy to make fp/fcl-image
somewhat
complete, they are also very memory hungry and slow.
IIRC I accelerated loading/saving simple 8-bit BMP images
20 to 50 times in
my work code.
Do you care to share some insights about what you did to accelerate it?
It is really very easy to accelerate it:
* Create a TFPCustomImage descendant that is limited to the bit depth you need.
* Do not use palette.
* Implement GetPixel and SetPixel so they convert from 64-bit from/to the depth
you used
* Implement a GetScanLine/SetScanLine specific to your bit depth.
You can now load/save the image very fast using the GetScanLine/SetScanLine,
and all other FPIMage operations will work equally well.
Following prior discussions on the list, I have a sample implementation
ready (simple RGB, no alpha), but it is not yet committed.
It's maybe 20 lines of code.
I'll try and commit it tonight.
Michael.
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